All Modes Low Rec High
Failures/10^6 hours 0.31 1.71 21.94
Failures/10^6 cycles 0.11 0.75 1.51
Repair time (hours) 0.3 0.74 1.3
Failures/10^6 hours
Failure mode Low Rec High
Catastrophic 0.13 0.7 9
Zero or maximum output 0.06 0.31 4.05
No change of output with change of input 0.01 0.04 0.45
Functioned without signal 0.03 0.18 2.34
No function with signal 0.03 0.17 2.16
Degraded 0.14 0.75 9.65
Erratic output 0.03 0.17 2.22
High output 0.03 0.15 1.93
Low output 0.01 0.06 0.77
Functioned at improper signal level 0.05 0.29 3.67
Intermitted operation 0.02 0.08 1.06
Incipient 0.04 0.26 3.29
Note: Rec refers to the ‘Best estimate’.
Low, High refers to the best and worst data points (i.e. this establishes the range)
Table 5.3: Reliability data for temperature instruments, controls and sensors, Stewart and Melchers
(1997) (Source: adapted from IEEE (1984)).
Environmental Stress Modifier for failure rate
High temperature x 1.75
High radiation x 1.25
High humidity x 1.50
High vibration x 2.00
Table 5.4: Environmental modification factors for temperature instrument, control and sensor
reliability data to be multiplied on the failure rates in Table 5.3 depending on the
environmental stress. Stewart and Melchers (1997) (Source: adapted from IEEE (1984)).